The present invention relates to a module correcting pitch between documents traveling in a high speed mass mail processing and inserting system. The term xe2x80x9cpitchxe2x80x9d refers to the spacing between documents traveling in an inserter system. Properly controlled and predictable document pitch is necessary for reliable operation of such high speed inserter systems.
Inserter systems such as those applicable for use with the present invention, are typically used by organizations such as banks, insurance companies and utility companies for producing a large volume of specific mailings where the contents of each mail item are directed to a particular addressee. Additional, other organizations, such as direct mailers, use inserts for producing a large volume of generic mailings where the contents of each mail item are substantially identical for each addressee. Examples of such inserter systems are the 8 series and 9 series inserter systems available from Pitney Bowes Inc. of Stamford Conn.
In many respects the typical inserter system resembles a manufacturing assembly line. Sheets and other raw materials (other sheets, enclosures, and envelopes) enter the inserter system as inputs. Then, a plurality of different modules or workstations in the inserter system work cooperatively to process the sheets until a finished mail piece is produced. The exact configuration of each inserter system depends upon the needs of each particular customer or installation.
Typically, inserter systems prepare mail pieces by gathering collations of documents on a conveyor. The collations are then transported on the conveyor to an insertion station where they are automatically stuffed into envelopes. After being stuffed with the collations, the envelopes are removed from the insertion station for further processing. Such further processing may include automated closing and sealing the envelope flap, weighing the envelope, applying postage to the envelope, and finally sorting and stacking the envelopes.
An inserter system may typically include a right angle transfer module to perform a 90-degree change of direction of documents flowing through the inserter system. The right angle transfer module allows for different configurations of modules in an inserter system and provides flexibility in designing a system footprint to fit a floor plan. Such a right angle transfer module is typically located after the envelope-stuffing module, and before the final output modules. Right angle transfer modules are well known in the art, and may take many different forms.
During processing, envelopes will preferably remain a regulated distance (or xe2x80x9cpitchxe2x80x9d) from each other as they a transported through the system. Also, envelopes typically lie horizontally, with their edges perpendicular and parallel to the transport path, and have a uniform position relative to the sides of the transport path during processing. Predictable envelope positioning helps the processing modules perform their respective functions. For example, if an envelope enters a postage-printing module crooked, it is less likely that a proper postage mark will be printed. For these reasons it is important to ensure that envelopes do not lie askew on the transport path, or at varying distances from the sides of the transport path.
For this purpose, envelopes, or other documents, are typically urged against an aligning wall along the transport path so that an edge of the envelope will register against the aligning wall thereby straightening the envelope and puffing it at a uniform position relative to the sides of the transport path. This aligning function may be incorporated into a right angle transfer module, whereby a document may impact against an aligning wall as part of performing a 90-degree change of direction.
Typically the envelope edge that is urged against the aligning wall is the bottom edge, opposite from the top flapped edge of the envelope. Thus after coming into contact with the aligning wall and being xe2x80x9csquared up,xe2x80x9d the envelope travels along the transport path with the left or right edge of the envelope as the leading edge.
The action of impacting the bottom edge of the envelope against the aligning wall may also serve the purpose of settling the stuffed collation of documents towards the bottom of the envelope. By settling the collation to the bottom of the envelope it is more likely that no documents will protrude above the top edge of the envelope, and that the envelope flap can be closed and sealed successfully.
Current mail processing machines are often required to process up to 18,000 pieces of mail an hour. Such a high processing speed may require envelopes in an output subsystem to have a velocity as fast as 85 inches per second (ips) for processing. Envelopes will nominally be spaced 200 ms apart for proper processing while traveling through the inserter output subsystem. At such a high rate of speed, system modules, such as those for sealing envelopes and putting postage on envelopes, have very little time in which to perform their functions. If spacing is not maintained between envelopes, the modules may not have time to perform their functions, envelopes may overlap, and jams and other errors may occur.
For example, if the space between contiguous envelopes has been shortened, a subsequent envelope may arrive at the postage metering device before the meter has had time to reset, or perhaps even before the previous envelope has left. As a result, the meter will not be able to perform its function on the subsequent envelope before a subsequent envelope arrives, and the whole system may be forced to a halt. At such high speeds there is very little tolerance for variation in the spacing between envelopes.
Other potential problems resulting from excess variation in distance between envelopes include decreased reliability in diverting mechanisms used to divert misprocessed mail pieces, and decreased reliability in the output stacking device. Each of these devices have a minimum allowable distance between envelopes that may not be met when unwanted variation occurs while envelopes travel at 85 ips.
Jam detection within the aligning module may become difficult to manage as a result of excess pitch variation. Jam detection is based on theoretical envelope arrival and departure times detected by tracking sensors along the envelope path. Variability in the aligner module will force the introduction of wide margins of error in the tracking algorithm, particularly for start and stop transport conditions, making jam detection less reliable for that module.
Pitch variation occurs for a number of reasons. One source of variation can be an aligner module for a high-speed inserter system, as described above. As envelopes in a high speed mailing system impact the conventional aligner wall, the impact causes the envelopes to decelerate in a manner that may cause the gap between envelopes to vary as much as +/xe2x88x9230 ms. While such a variation might not be significant in slower machines, this variation can be too much for the close tolerances in current high speed inserter machines.
In addition to variation resulting from impacts at the aligner module, variation may be the result of xe2x80x9cditherxe2x80x9d in the transport of stuffed envelopes. Different envelopes may be stuffed with different quantities of sheets that form the individual mail pieces. As a result, envelopes will vary in weight. Such variation in weight will cause envelopes to have different acceleration, momentum and frictional forces acting upon them as they are transported in the inserter output subsystem. For example, different envelopes will experience different slippage as transport mechanisms such as rollers and belts are used to transport them. Accordingly, such dither may result in an additional +/xe2x88x9230 ms variation in the spacing between envelopes.
The problem of non-deterministic behavior at the aligning module is addressed in a co-pending patent application entitled DETERMINISTIC ALIGNER FOR AN OUTPUT INSERTER SYSTEM, by John Sussmeier, filed on Oct. 18, 2001, Ser. No 09/981,959 and commonly assigned to the assignee of the present application. That application is hereby incorporated by reference in its entirety. The aligner system described in that application may be used in conjunction with the system described in the present application in order to minimize variation in spacing between envelopes traveling in an inserter output subsystem.
The present application describes a system and a method to reduce variation in envelope pitch to further meet the needs and shortcomings of the conventional art described above.
The present invention addresses the problems of the conventional art by providing a pitch correcting module (xe2x80x9cPCMxe2x80x9d). The pitch correcting module is positioned upstream of modules that are sensitive to variation in pitch, in order that such variations may be corrected before the envelopes reach those modules. The pitch correction module includes a transport mechanism, such as hard nip rollers, or conveyor belts, to speed up or slow down the transport of envelopes in order to correct pitch variations. The relative spacing of envelopes is preferably detected by sensors which sense envelopes entering and leaving the pitch correcting module. Based on input from the sensors, a processing device controls the transport mechanism of the PCM to speed up or slow down the envelope in accordance with a predetermined algorithm.
The pitch correcting module is dimensioned to accommodate the varying envelopes sizes that the inserter system is designed to process, while at the same time maintaining the capability of the inserter system to operate at its designed speed, and to correct the range of expected unwanted variation. The PCM is also designed to provide the necessary accelerations and decelerations to achieve corrections within a range of expected pitch variations.